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This is about science produced by the California Institute of Technology and originally broadcast by station KPCC in Pasadena California. The programs are made available to this station by national educational radio. This program is about life on Mars. Meeting to discuss this subject are Dr. Robert McGregor of Cal Tech's Jet Propulsion Laboratory and his guest Dr. Norman Horowitz professor of biology. Here now is Dr. McGregor Lee and the National Aeronautics and Space Administration has indicated that one of its prime goals in its space program is the search for life in the solar system. The National Academy of Sciences has also in a recent position paper indicated a strong encouragement and support of this objective. Now we recognize that both groups represent a limited part of our society and that their scientists and technologists and therefore have a particular point of view. A new norm in your opinion as a biologist think that this
objective is well supported or and I tracked of one to the society at large. Yes I do. Our use is a scientific and technological age and I think the scientific and technological spirit motivates all people in Western society not only professional scientists but people in general. Well we know of course that in past civilizations there have been great driving forces which have led a particular segment of the human species on for centuries in search of a particular objective. Do you think that perhaps this search for a life in extraterrestrial terrain might gain such and such an acceptance. Yes I do. Certainly almost everyone you talk to is interested in the question. Life on Mars or life on other planets. It's a question that is not only of enormous scientific interest but of course it would
have profound philosophical implications that would affect our thinking about ourselves in many ways. You mention Mars. Is this in fact one of the places that one would think of looking first in the solar system or are there other places that might be more attractive or more exciting as a prospect. Well Mars is the best prospect at the moment. There are closer places to the Earth and Mars where one might think first of looking for life the moon of course is the closest body closest to the earth in the solar system. And next to the moon is Venus. But both of these extraterrestrial bodies have been excluded for various reasons as. Possible habitats of life as well as the moon for example entirely out of the question as a possible mode environment for living things. I think it is because the moon has virtually no
atmosphere. There are no indications of any water on the moon of any carbon dioxide and without an atmosphere it's difficult to see how any life could survive or even the most elementary forms. That's right about Venus Venus has a very thick atmosphere heavy atmosphere and Venus is also the same size as the earth. It's the closest planet to the earth in the solar system and one might think that Venus is a suitable abode for life. It's certainly in the past as seen to be an exciting possibility. Course we read about it in fiction and all that what's made it less attractive today. Well as you well know as a result of the Mariner 2 flyby havingness. This in one thousand sixty three. And as a result of astronomical observations from the earth we now know that the surface temperature of Venus is very high. The temperature
on Venus. It turns out is around 400 degrees centigrade. That would be seven to eight hundred degrees Fahrenheit. And this is this is such a high temperature that organic compounds upon which this structure of living organisms depends. These organic compounds are unstable at this high temperature and it's inconceivable that there could now exist on Venus any form of life although it's not excluded that Venus may at one time before it became so hot may have supported life. Well you mentioned some of the recent astronomical observations and also the results of the Mariner 2 which were well from you with. But I notice that there is still some element of opinion in our scientific community that this may not in fact be a real temperature but rather so-called brightness temperature which may be due to other effects than the physical thermal temperature. Yes that's correct and entirely out of the question. There is a residue of doubt and there always will be about the surface temperature of Venus until we actually land on the planet. Or
until we know in detail the structure of the Venus atmosphere. Our evidence at the moment is based on indirect kinds of measurements. But most astronomers that I talk to are convinced that the surface temperature is quite high although the possibility of mountain peaks of cooler temperatures is not yet excluded. This would give us some possibility then. I notice that by from some of the recent radar measurements that have been made that there is a suggestion that perhaps there are some unusual features on the planet which might be attributed to a higher elevation. Elevations than the norm and perhaps this might be a possibility. However the atmosphere it's off in the upper regions where it might be cooler. Well it has been suggested that life might survive in the clouds of Venus which as I've already mentioned are very thick and this is conceivable but
it's very speculated there would presumably be sufficient water vapor in the clouds to support life and carbon dioxide which we know of bounds on Venus and there would be sunlight these are the three major requirements for life. Carbon dioxide water and light but still life would also require small amounts of mineral elements and how these would be transported to organisms living in the clouds is hard to imagine. So all this put together then. We still think that Mars would be a more attractive possibility Left-Right Mars is more attractive at the moment than Venus I wouldn't want to erase Venus completely from our future thoughts and ideas and comments we do not have to the physical environment of Mars. Well from the point of view of biology the physical environment of Mars can be described in one word it's hostile by terrestrial standards. First of all Mars is very cold compared to the earth. The temperature on Mars is
the mean temperature on Mars about minus 15 degrees excuse me minus 55 degrees centigrade as compared with about plus 15 degrees centigrade for the earth. Furthermore Mars is a very dry planet. There's no liquid water on Mars water that exists on Mars exists only as ice or as water vapor. But those conditions do not sound so severe that one couldn't find similar places on the earth and yet we seem to have an abundance of life no matter where we go. Yes there are of course very dry regions of the earth and there are very cold regions of the earth and possibly the most Mars like region on earth is the Antarctic. A continent which we're just beginning to explore the Antarctic is thought by most people to be a very wet continent since it's covered by ice. But
in fact there are drive alleys in Antarctica where the annual precipitation is very low and where temperatures are very low. And if these drive valleys biological studies would be of great interest and we are planning during the next Antarctic summer to send a number of our people from the Jet Propulsion Laboratory to collect samples in the DR valleys of Antarctica to carry out a micro biological study. How about the mountainous regions in the earth. Are these provide similar kind of terrain in terms of temperature and certain pressure variations that one might find. Yes also the high dry regions in Asia would possibly be useful. But in the Western Hemisphere other places around here that are similar. Well of course we have the deserts of Southern California which are very dry although they're much. Wetter
than Mars and even Southern California is not as dry as Mars. There's a desert in Chile that chilly out a common desert where it is said that no rain has fallen in. In living memory we have a number of people from the Jet Propulsion Laboratory going there next month to collect some samples to study the microbial life in the desert soil. There is some experience with that already norm. What sort of results have we gotten from these Mars like the terrain. Well from the Chilean Atacama Desert where from which we got some samples last year it appears that there are microorganisms growing in the air at least existing in the soil. The pictures of the desert show that it's totally devoid of any visible vegetation. Nevertheless if you if you scrape up the soil and culture the soil under correct conditions then you can detect an abundance of microbial life.
And the question is whether this life resides in this soil or whether it's just been blown in. And the evidence suggests that it's that it's living there because it prefers a medium whose chemical composition resembles the soil in which it's found. We've been talking about the temperature variations and the dryness are there any other factors in the Martian and environment which give it the dissimilarity or similarity to earth. Well it's dissimilar in a number of ways. In the first place no oxygen has ever been detected in the Martian atmosphere. The Martian atmosphere is principally carbon dioxide this is an important difference from the earth. Second important difference is the fact that the Martian atmosphere is very thin compared with that of the earth. The surface pressure of the atmosphere at the surface of Mars is only about one percent of the pressure of our own atmosphere here on the earth. This fact means that. The surface of Mars is being
constantly bombarded with cosmic rays for example from outer space. We don't have the shielding of our own atmosphere is what that's right we have a shield here of 15 pounds per square inch of atmosphere and Mars. Mars lacks much of this. Not that Mars does not have a magnetic field according to the Mariner 4 flyby are certainly very small and are a very small one and the magnetic field of the earth is also an important protective mechanism against cosmic radiation. We certainly got a lot of things working for us no. Yes yes we do happen to live in a very accommodating planet or else we become of it ourselves to the environment that exists that that's a and important observation. How about the other forms of radiation. There are other forms of radiation reach the surface on Mars because of the composition and thinness of its atmosphere and the biologically most harmful form is ultra violet light from the sun.
Here on the earth most of the ultraviolet is screened out by the ozone which exists high up in our atmosphere. But Mars has no it was only air and presumably they saw or ultraviolet reaches the surface in an attenuated intensity. At least so far as we know now so far as we know now I guess the press is important to note that you indicated earlier that carbon dioxide was a prime constituent which is the one species that we recognized from spectroscopic observations ground based observations. It's not entirely out of the question that there might be other chemical species present which we've not been able to detect. Yes well in fact water vapor has also been detected. You know that really small it was in the Martian atmosphere and it's quite conceivable that there are other compounds gases in that atmosphere that have not yet been detected. I should say before we leave this subject that although the radiation that reaches Mars is inimical
to life in general it is not of such intensity that it would make life impossible on Mars. The cosmic ray intensity on Mars although it's several hundred times that on the earth is still far below a level that would be dangerous for life. How about the ultraviolet and the U.V. is it is a more important question since the flux of ultraviolet on the surface of Mars is about what you would get from a sterilising lamp. It's a very intense radiation but fortunately Violet is easily absorbed by many kinds of chemical substances. So that it would be. An easy matter for a Martian species to protect itself by producing a screen of some kind of fur or hair or skin of some kind that would filter out the ultraviolet before it got inside. Well you paint a picture here of the Martian terrain as being very low
pressure such as a high mountain top very high mountain top cold as perhaps the Antarctic is cold and dry at all attractive in fact you used the word hostile. What makes you think that there might be something there at all and that kind of a situation. Well I think the chances of there being life on Mars are certainly not very high nevertheless. Everything that we know about Mars although it's hostile nothing excludes the possibility that there is life on the planet. We have very dry environments on the earth and we find when we go into these environments that there are species that are adapted to live in these very dry environments. And the more advanced or complex than the microbial Yes the species that they're best adapted actually did live in very dry conditions are our mammals for example the Mojave desert here in Southern California has a number of drought loving species. One of them the
kangaroo rat has been studied extensively by Schmidt Nielsen who was a well-known physiologist. Schmidt Nielsen has found that the kangaroo rat can live indefinitely without ever drinking water. It produces all of its water by the combustion of carbohydrates. That is it's metabolically produced water and even in nature the kangaroo rat never eats succulent leaves it prefers dried up stems and roots. So it's not really out of the question that such things and such a living species might be present even a very dry climate. We were hoping here and not too distant future to approach Mars in particular to attempt some experiments on a surface. One of the prime questions that I want to attempts to answer here I presume to ask is there anything living. Yes that would be the first question of course is there anything alive a tall on Mars. The second question and equally important in my mind would be to
learn whether or not this Martian life if it exists has originated on Mars independently of life on the earth in other words the basic question is has life originated more than once in the solar system. And to answer this second question would require careful chemical study of the nature the chemical organization of Martian life. So the order of business would be to first detect some life and then attempt to determine its chemical character and organization to see if it has any connection to life as we know it here. That's right. Well what sort of things would you look for and how would you attempt to relate this to life as we know it on the earth. What are the characteristics as you might say. Well the the most important chemical substances in terrestrial life are the genes and enzymes the genes are the substances in our cells that carry our heredity and the enzymes are the
substances which carry out the chemical transformations in living organisms. All terrestrial life contains genes that are made of nucleic acids. So that's a key there and that's a key there and all the enzymes interest you know organisms are proteins. And these nucleic acids and proteins have very characteristic chemical compositions. And the first thing one would like to know about Martian organisms if there are such things is what are the chemical compositions of its genes and its enzymes. Would you in fact look for proteins. Yes one would look for nucleic acids and proteins in devising experiments or techniques for making such measurements. I'm sure there must be many complex approaches that one can use here. I would guess that the most simple minded ones are most foolproof ones would be the approach is that you'd
want to take first. Yes. Course one of the first things I want to I want to do in sending biological experiments to Mars is to find the experiments that are most likely to yield answers definitive answers of one kind or another. And I suppose that most people would agree that of all the experiments one can think of it television pictures would be the most convincing if certainly if you saw something walking by. That's right. And so a good television photography has a high place in our list of possible life detection experiments from Mars. But as you well know to transmit television pictures over the distance from Marcy Earth requires large amounts of power and we may not have enough power on early missions to send many television pictures and so we're also interested in designing experiments that can give us results with less consumption of power.
I should think too that in looking at images an attempt to identify objects or things that might be related to life or in fact life forms in themselves. One would have to have some sort of code. I mean we are after all experienced when we look at a picture and we say yes indeed this is a leaf from a tree or this is something else. If you look an entirely air alien environment how could you say that this is indeed a living thing and this is a rock or a mineral or could you be certain in that sense. No I don't think you could be certain I don't can't imagine any single experiment it would be. Tell us with certainty that if an object we see is going to have to be on a macroscopic scale. That's right in a large scale. Yes it would have to have a regular shape that we could not easily imagine had arisen by our random processes. How about chemical techniques other specific analytical methods that one can use here and what might be some of the possibilities that have been considered.
Well among the possibilities are a chemical analysis of the atmosphere of Mars. There are arguments which show that it may be possible to detect life on Mars simply by understanding the chemical composition of the atmosphere. Well the atmosphere is a can be regarded as a large sewer into which the products of biological activity are poured and it's also a substrate and from which the organisms draw their. Automatically their nourishment so that the composition of the atmosphere will be affected in one way or another by the existence of life and our own atmosphere is strongly influenced by the fact that we have living organisms on the surface so that there's a certain character in our own atmosphere and you would expect so on Mars which is determined purely by the presence of living things that's right and they could not be explained in any other way. That's right there's a certain balance you're saying. That's right. That's right. Our atmosphere is not in chemical equilibrium. And the
reason it is not is because we have living organisms on the surface that are constantly dumping things into That's right. I remove ing other things. So you could look at the atmosphere and specific chemical ways. And from this determine whether or not it's in chemical equilibrium I say right. How about some of the techniques and other techniques that are being considered our chemical analysis of Martian soil to detect the presence of organic compounds because that's necessary condition but not a sufficient one. That's right. And still other kinds of experiments that are being studied are those in which attempts will be made to culture that is to grow microorganisms from Martian soil samples were specially interested in microorganisms because we know that on the earth microorganisms occur almost everywhere. They're very hardy. They live in the most extreme environments on the earth and we
suppose that if there's life on Mars there will certainly be microbial life of some kind only the most elementary kind. Yes there may be no other form of life on Mars but if there's any life at all there should be microbial life. Well I'm a little bit troubled though at the idea of growing or attempting to cultivate the microorganisms that you might find on Mars how on earth do you know what they like. Well sort of assuming isn't it that their chemistry is similar or that they like the same goodies that our bacteria do. Yes well there are reasons for assuming that their chemistry will be similar. One important reason is that an examination of the chemical elements shows that carbon is the only element which is suitable for building up the large and complex kinds of molecules upon which we think living processes must depend. So you think there's a strong chance that if there's something living on Mars it would have a carbon chemistry.
Yes. There's strong reasons to believe that. And there are other ways of deciding what kinds of foodstuffs a Martian organism might might like. The There's a famous experiment for example it was carried out a number of years ago by Stanley Miller and Harold Urey in which they showed that if a mixture of simple gases for example methane ammonia water vapor and hydrogen mixture which is believed to correspond to the primitive atmosphere of the planets if such an atmosphere is irradiated by a spark discharge or by a violet radiation organic compounds are produced and among these organic compounds are many which are of biological interest compounds which are. Incorporated in present day living organisms and which serve
as substrates and as nutrients for organisms on the earth. And so we imagine that the same process occurred on Mars that its primitive atmosphere was irradiated by solar ultraviolet and that these same compounds were precipitated on of the surface of Mars as we believe they were on the surface of the earth. So then by knowing this or is making Just promise that you can prepare a soup that the bacteria there will enjoy and therefore grow and be measurable. At least this seems to be a reasonable assumption at the moment. Are there any other specific things that one might do here. Yes there are other kinds of metabolic experiments that one could carry out to detect microbial life. A very important one is the detection of photosynthesis. Photosynthesis is a process that's carried on by green plants in which they fix atmospheric carbon dioxide and produce organic compounds from it. Well there are many microorganisms on the earth which do the same
thing and photosynthesis is a fundamentally important process. If there's any life on Mars there must be at least one photosynthetic species since all of the energy must ultimately come from the sun. There must be at least one species which can fix solar energy. So you could devise an experiment that would approach that kind of a situation as right we would. We would look for the light dependent fixation of carbon dioxide. And that's a relatively straightforward experiment I presume. Yes it is it can be done with radioactive carbon dioxide. So the picture that comes out of all this then is that although. Our nearest neighbors are not entirely our planetary neighbors are not entirely the most attractive environments that there's certainly one candidate which looks reasonably good. Mars it has an environment which is not unlike some of the more extreme situations on the earth where we know there are living things. But there are specific kinds of experiments that one could perform when one goes to Mars specific kinds of questions that one could
ask which would give definitive answers. So it looks as though one could map out a reasonable and rational course of exploration. Question is is the prospect of finding life the prime motivation here. I would say that the disaster in the search for extraterrestrial life is not based on optimism about the outcome it's based rather on the immense importance that a such a discovery would have. I personally don't think that the chances of finding life on Mars are very high. But I do think that it's important to get the answer. And what Mariner 4 showed us is that we now have the technology to get that answer. And I think we should pursue this to its logical conclusion. Well I think with that remark then we'll close. Thank you very much Norman. This was about science with host Dr. Robert McGregor Lee and his guest Dr. Norman Horowitz a professor of biology joined us again for our next
program went to more prominent scientists will discuss a subject of interest about science is produced by the California Institute of Technology and is originally broadcast by station KPCC in Pasadena California. The programs are made available to this station by national educational radio. This is the national educational radio network.
About science
About life on Mars?
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California Institute of Technology
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University of Maryland (College Park, Maryland)
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This program explores the quest to find life on Mars. The guest for this program is Dr. Norman Horowitz, California Institute of Technology.
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Interview series on variety of science-related subjects, produced by the California Institute of Technology. Features three Cal Tech faculty members: Dr. Peter Lissaman, Dr. Albert R. Hibbs, and Dr. Robert Meghreblian.
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Guest: Horowitz, Norman H. (Norman Harold), 1915-2005
Host: Hibbs, Albert R.
Producing Organization: California Institute of Technology
Producing Organization: KPPC
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University of Maryland
Identifier: 66-40-6 (National Association of Educational Broadcasters)
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Duration: 00:28:28
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